Is jelq exercise effective & safe?

Not effective. Others have answered similar questions on healthtap, replying that penile size is not likely to be increased through this method. Penis size is genetically determined, but can seem smaller if you have a fat abdomen. It's also possible to injure yourself while "jelqing." I have referred this question to urology colleagues in hopes of more astute replies.
No & No. I have very little experience with this but there is no reasonable data to show it helps. I have had one patient who came in with a fairly significant nerve injury from it so i would never recommend it. Your best bets are exercise and lose weight.